Method of making a ring

ABSTRACT

A method of making a ring comprising cutting a raw material stock to a predetermined length, cutting a slit through the raw material stock along its length to form a blank, inserting the blank into a tool, expanding the middle of the slit while simultaneously applying a compressive force to the ends of the blank, and expanding the middle of the slit until the blank is round.

FIELD OF THE INVENTION

The invention relates to a method of making a ring, and moreparticularly, to a method of making a ring by expanding the middle of aslit blank while simultaneously applying a compressive force to ends ofthe blank.

BACKGROUND OF THE INVENTION

Tubular rings are used for many applications in the industry. Rings canbe broached, hobbed, machined, ground, or used as is for manyapplications. Applications include gears, starter gears, clutch hubs,sprockets, pulleys, crankshaft dampers, and many other products.

There are many existing arts for manufacturing tubular rings. Somecommon methods include making a hoop from bar stock and welding thejoint; making a tube and cutting it; deep drawing a cup and removing theface of the cup; expanding a blank in ring rolling, forging, casting, orspinning a blank from sheet metal.

All of these processes are suitable, but the cost or quality of theproduced ring is always a problem. For example, welded hoops haveproblems in the weld area when the ring is flow formed further to makegears, pulleys, splined rings, etc. Further, the welding and cleaningthe weld and/or heat treating to normalize the weld area is costly.

Cut seamless tubes are expensive and making a cup in a press andremoving the face creates excessive waste.

Representative of the art is U.S. Pat. No. 4,590,780 which discloses aprocess starting from a pre-heated bar, there is sheared-off first aportion (41) which, in a first forming stage of the machine, is formedinto a tier shaped pressed article. In the second forming stage, thepressed article is further formed so that it has an inner ring (J), anouter ring (A) arranged co-axially to this and a radial annular web (S)connecting the two rings (J,A). The sheared-off outer ring (44) istherefore ejected in the next to last stage, while in the last workingstage the inner ring (45) separated from the outer ring is subjected tofurther working. This last working stage involves stamping out a wastepiece (35) and shearing-off an annular web (38). It is also possible tocarry out a forming operation in this last working stage to upset theremaining inner ring (22 a). By means of this process which provides forthe elimination of the finished outer ring (44) in the last workingstage, the radial annular web (38) can be supported over its fullcross-sectional surface during the shearing-off operation.

What is needed is a method of making a ring by expanding the middle of aslit blank while simultaneously applying a compressive force to ends ofthe blank. The present invention meets this need.

SUMMARY OF THE INVENTION

The primary aspect of the invention is to provide a method of making aring by expanding the middle of a slit blank while simultaneouslyapplying a compressive force to ends of the blank.

Other aspects of the invention will be pointed out or made obvious bythe following description of the invention and the accompanyingdrawings.

The invention comprises a method of making a ring comprising cutting araw material stock to a predetermined length, cutting a slit through theraw material stock along its length to form a blank, inserting the blankinto a tool, expanding the middle of the slit while simultaneouslyapplying a compressive force to the ends of the blank, and expanding themiddle of the slit until the blank is round.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate preferred embodiments of the presentinvention, and together with a description, serve to explain theprinciples of the invention.

FIG. 1 is a plan view of a blank.

FIG. 2 is a side of view of the blank in the tooling.

FIG. 3 is a side view of the blank in the tooling.

FIG. 4 is a perspective view of the blank at an intermediate step.

FIG. 5 is a side view of the blank in the tooling.

FIG. 6 is a perspective view of the finished ring.

FIG. 7 is a top perspective view of a blank in the tooling.

FIG. 8 is a top perspective view of the tooling.

FIG. 9 is a side perspective view of the tooling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention comprises a process of manufacturing a tubular ring frombar stock. Although a rectangular bar stock is preferred, any otherconfiguration (round, hexagonal, etc.) may also be used.

The manufactured ring may be used in making gears, pulleys, sprockets,bearing races, one-way clutch races crankshaft damper inertia rings andsimilar products.

FIG. 1 is a plan view of a blank. The process starts with a raw materialsuch as a simple bar stock from which is cut a blank 10 having thedesired length (L) and width (W). Raw materials may comprise other thanbar stock, including flats, rounds, or any other available form of metalmaterial. For the purpose of this example a rectangular bar stock isused. The four corners 11 at the ends of the cut rectangular blank arerounded using known processes to facilitate the process and to give theblank a uniform thickness.

The blank is cut to form a slit 12 in the middle extending in thelongitudinal direction (along its length). The slit can be cut using alaser or other cutting means which include but not limited to: highpressure water jet, laser, plasma, abrasive cutters, milling, or othermeans. At each end of the slit is a radius 13 to prevent crack formationin the expansion process and to keep the thickness uniform. The width ofthe slit is kept to a minimum to reduce waste.

FIG. 2 is a side of view of the blank in the tooling. The blank 10 isthen introduced into a press. A contoured thickening and rounding post20 is pressed into the blank at the slit which opens and expands theslit. The post initially contacts the slit in the middle.

End 22 of post 20 comprises a blade which engages the slit 12. Post 20is pressed though blank 10 into a receiving female die 21 using a knownhydraulic ram 200.

Use of a lower support die 21 that is as large as the final size of theID of the ring, the blank will expand to a certain extent, about 50%,but it tends to bend and does not continue to expand in a single plane.Therefore, in order to have proper support for the blank as it is beingexpanded and to prevent it from bending during forming, either anexpandable (sliding) lower tooling support tooling or a multi stationtooling with gradually larger lower tooling opening and thicker androunder post may be used as described herein.

The maximum outside diameter of the post 20 substantially matches thedesired inner diameter of the finished ring, see FIG. 6, minus anymachining that may be required.

FIG. 3 is a side view of the blank in the tooling. Since tensile forcesare not desirable in metal forming and compressive forces are desirable,in order to prevent pulling the ends apart and causing failure theinstant process pushes, that is, applies a compressive forcesimultaneously to the ends of the blank as it is also being expanded bythe post 20.

Applying compressive forces to ends 101, 102 of blank 10 while drivingthe post 20 into the slit gradually forms the blank into a round ring.The compressive force is applied to ends 101, 102 of the blank throughshoes 23, 24. Shoes 23, 24 are pressed by known hydraulic rams 201 and202 in a manner known in the art.

FIG. 4 is a perspective view of the blank at an intermediate step. Slit12 is shown partially opened. The full diameter of post 20 has not yetengaged the blank 10 and so it is not yet fully rounded. Shoes 23, 24engage ends 101, 102 of the blank.

FIG. 5 is a side view of the blank in the tooling. The full outsidediameter of post 20 is shown fully engaged with the blank 10. Blank 10is therefore fully round. Shoes 23, 24 are pressed about blank 10 inorder to control the forming and to avoid “squaring” of the blank.

FIG. 6 is a perspective view of the finished ring. The ID of ring 10substantially matches the OD of the post 20.

Once the ring is formed on the post, it is ejected and it is ready touse. If desired and required it is ready for final operations, forexample, machining, rolling, spinning, forging, sizing, grinding, etc.The formed ring can then sized in an ironing die in a press to obtain avery accurate size and/or a very fine surface finish.

Yet another version of the method shows that the blank can be expandedto the somewhat square shape and then rounded in a simple rotary forgingoperation. Other embodiments include taking the square blank andspinning it into a round ring, or using a ring rolling process toachieve a round ring.

Further, the ring can either be formed to a round final shape, or it canbe introduced to the press tooling again for a final sizing and roundingoperation. The need for these additional operations increases as hardermaterial is used, e.g., alloy steels or high carbon steels. Hardersteels can be formed with the described press tooling, but, they mayrequire larger diameters at the end of the inner slit to preventcracking. They may also require hot forming (usually 600 to 1100 degreesCelsius), or warm forming (up to 600 degrees Celsius).

The geometrical aspects of the parent bar stock, namely the length,radii around the outer edges, the diameter of the rounded radii at theends of the slit and the slit thickness are all relevant variables whichcan be easily selected to optimize accuracy with minimum offal.

The design of the tooling is also relevant to reduce complexity. Thetooling can comprise one long post with an expandable lower tooling or afew press stations with gradually expanding lower tooling and graduallythickening and rounding upper tooling. Furthermore, to prevent failureat the ends of the slit for very hard material, the pre-form blank maybe made in a “dog bone” shape, where very large diameters at the ends ofthe slit will allow an easy forming process at the ends of the slitarea.

FIG. 7 is a top perspective view of a blank in the tooling. Blank 10 isshown staged in collar 25. Collar 25 controls the position of the blankprior to and during the forming process. Shoes 23, 24 are each shownwithdrawn in order to allow blank 10 to be inserted between. Members 27,26 support the blank between shoes 23, 24.

Shoes 23, 24 in FIGS. 7, 8, 9 are the same as those shown in FIGS. 2, 3,5.

FIG. 8 is a top perspective view of the tooling. Blank 10 is removed togive a better view of the members 26, 27. Members 26, 27 apply a forcein a vector direction normal to the compressive force vector of shoes23, 24 and simultaneously withdraw, or move apart from each other inconcert with post 20 as post 20 is pressed through the slit in blank 10.This provides the necessary support for blank 10 as it is formed. Putanother way, members 26, 27 support the blank to prevent an axialdeformation that is normal to the direction of expansion of the slit.This prevents the blank from deforming in the direction of movement ofpost 20. The movement of post 20 is characterized as movement in anaxial direction.

FIG. 9 is a side perspective view of the tooling. Post 20 is shown atthe beginning of insertion into slit 12. Blade 22 is shown engaged withslit 12. Post 20 is pressed into slit 12, thereby expanding the middleof the slit while shoes 23, 24 simultaneously compress the ends of theblank. Post 20 is pressed into the blank 10, thereby continuing toexpand the middle of the slit until the blank is round. Post 20 is thenwithdrawn and the formed ring is ejected.

Although forms of the invention have been described herein, it will beobvious to those skilled in the art that variations may be made in theconstruction and relation of parts without departing from the spirit andscope of the invention described herein.

1. A method of making a ring comprising: cutting a raw material stock toa predetermined length; cutting a slit through the raw material stockalong its length to form a blank; inserting the blank into a tool;expanding the middle of the slit while simultaneously applying acompressive force to the ends of the blank; and expanding the middle ofthe slit until the blank is round.
 2. The method as in claim 1 furthercomprising supporting the blank in a direction that is normal to thesimultaneously applied compressive force.
 3. The method as in claim 1further comprising cutting a radius at each end of the slit.
 4. Themethod as in claim 1 further comprising: ejecting the formed blank fromthe tool; and finishing the formed blank to a final size and form. 5.The method as in claim 1 further comprising supporting the blank toprevent an axial deformation that is normal to the direction ofexpansion of the slit.